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Audie Cornish speaks with Dr. H. Jay Zwally, a NASA glaciologist, about the latest break of ice off of the Petermann Glacier in Greenland.

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From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

AUDIE CORNISH, HOST:

And I'm Audie Cornish. This week, a NASA satellite spotted a new iceberg broken from an ice sheet in Greenland known as the Petermann Glacier. The iceberg is twice the size of Manhattan, 46 square miles; and it's the second time in the last few years that an island-sized chunk of ice has calved from the glacier.

To find out more about this event, we turn to Dr. Jay Zwally. He's a glaciologist with NASA's Goddard Space Flight Center. Dr. Zwally, welcome.

DR. H. JAY ZWALLY: Good afternoon.

CORNISH: So, how common is it for chunks of ice this large to break from glaciers?

ZWALLY: Well, they break periodically, at the front. But what is happening in Petermann Glacier is that large chunks are breaking off so the front is actually moving backward. And if this continues, the floating part of the glacier will eventually disappear.

CORNISH: And this isn't the first time, though, that an iceberg has split from this particular glacier. So what's significant about the break?

ZWALLY: Well, it's a sign that the tongue is actually breaking up and going to disappear. We believe it's due to warmer water coming into the seas around Greenland.

CORNISH: Now, people can go to our website to see some of the images of this. But can you describe to me, what does the Petermann Glacier really look like?

ZWALLY: Well, I'm looking at a picture right now, and it's actually a long extension. It looks like a tongue. It has a lot of cracks on the surface. It's a very rough surface because as the glacier flows from the land, there's a lot of crevassing. And at the end of it, you have icebergs, which are forming and going into the ocean. There's some sea ice there right now - in the pictures.

CORNISH: Now, researchers seem to keep a pretty close eye on the Petermann Glacier, generally. I mean, there's data going back - right? - more than 100 years. Why does this glacier garner so much attention?

ZWALLY: Well, because this had been happening to a lot of other glaciers farther south - like the Jakobshavn Isbrae glacier, starting in 1996. That's on the west side of Greenland, about halfway up. The floating part of that disappeared within a few years. And after that disappeared, the ice floe behind it, flowing into the ocean, sped up.

CORNISH: So where does this huge iceberg go now? I mean, does it just float off into the Atlantic?

ZWALLY: Well, it's going to float down along the west coast of Greenland. It'll be melting as it goes, and it'll probably flow into the Atlantic south of Greenland; maybe go down along Newfoundland, or maybe turn eastward and go into the Atlantic Ocean.

CORNISH: Any concerns about it crossing shipping lanes, or any of us interacting with it?

ZWALLY: Well, yes. It is a danger to shipping. It was an iceberg that came off of Greenland and sank the Titanic. But the Coast Guard keeps track of these, and it's very unlikely that a ship will run into it.

CORNISH: Give us some context. Do scientists believe that these big pieces of the Petermann Glacier are breaking off because of climate change?

ZWALLY: Well, I think it is. And the reason is that the warmer water has been coming up along the west coast of Greenland. And this warmer water is the result of the warming of the ocean and the Atlantic. And we believe that that is definitely climate change interacting with the glaciers.

CORNISH: Well, Jay Zwally, thank you for explaining it to us.

ZWALLY: You're quite welcome.

CORNISH: Dr. Jay Zwally studies glaciers with NASA. He was speaking with us about the latest iceberg to break from the Petermann Glacier, in Greenland.

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